Glomerular filtration rate (GFR) decreases with advancing age, particularly in men, although the rate of decrease in GFR is highly variable. Renal vasoconstriction contributes to the decrease in GFR because of increased renal nerve activity, angiotensin II, endothelin, and decreases in vasodilatory prostacyclin levels. Intrarenal nitric oxide activity may be enhanced during aging, perhaps as part of a compensatory response. The atrial natriuretic peptide system is altered during aging, but there is probably no net change in intrarenal hemodynamic actions. Glomerular damage also contributes to age-dependent decreases in GFR. The primary mechanisms are unknown, but they involve a buildup of mesangial extracellular matrix materials. Increases in vasoconstrictor, growth promoting factors, and/or decreases in vasodilator, growth inhibiting factors may contribute. Androgens provide a risk factor. Glomerular hypertension and/or hypertrophy are not primary factors in the development of age-dependent glomerulopathy, but will worsen the process when present.